Birds & bugs

Fowl play? (sorry…)

Poor old poulty and fowl, it’s not been a good couple of weeks for them. Early last week, news of bird flu hit the headlines, and yesterday, Campylobacter is causing concern. The Guardian calls it the “Dirty chicken scandal“, and one food expert has called for a boycott of chicken.

So what is all of the fuss about? Well the Food Standards Agency (FSA) has today published the results of a survey which has looked at levels of Campylobacter in chicken from supermarkets. In a nutshell (or should that be an eggshell…?), the FSA have sampled almost 2000 chickens that have been bought from various retailers and then tested them to see if they contain Campylobacter bacteria. Their results show the following:

70% of chickens that were tested were positive for the presence of Campylobacter

18% of chickens tested positive for Campylobacter above the highest level of contamination*

6% of packaging tested positive for the presence of Campylobacter

Only one sample of packaging tested positive at the highest level of contamination*

* Above 1,000 colony forming units per gram (>1,000 cfu/g). These units indicate the degree of contamination on each sample.

Campylobacter are a type of bacteria that are naturally found in chickens, cows and other animals, and which can infect humans. These bacteria cause a type of stomach complaint called gastroenteritis. This usually entails fever, cramps and diarrhoea which is usually unpleasant, and can be bloody. However, the infection usually clears up by itself, without any treatment.

How were the experiments done?

Chickens were collected from retailers and taken to the laboratory where samples were taken before expiration of the ‘best before date’. Two samples were taken: a 25 g sample of skin, and a swab of the packaging. Samples were plated on culture medium which was selective for Campylobacter, incubated to allow bacteria to grow, and then the number of bacteria were counted and recorded.

What does it mean?

The number of Campylobacter bacteria you need to consume to become ill is called the infectious dose. For Campylobacter, this is thought to be as low as 500 bacteria. This means that if you ate some raw chicken that contained 1000 cfu/g of Campylobacter, you would have a reasonable risk of becoming ill. However, these bacteria are readily killed by heat, so as long as chicken is cooked properly, there should be no problem. And of course, good hygiene practices in the kitchen will help to minimise the spread of bacteria.

Where do I find more information?

If you want to know more about food poisoning, you can find information here. Further information about Campylobacter is available here.

[Note: A cfu, or colony forming unit, is the unit we use to quantify the number of bacteria. When bacteria grow, a single cell divides until a clump of cells called a colony forms. Because we can’t see individual bacterial cells with the naked eye, we use colony forming units as the measure, on the assumption that a single cell gives rise to a single colony forming unit.]